2024-03-28T15:15:57Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/128852021-06-14T09:26:43Zcom_10261_50com_10261_8com_10261_83col_10261_303col_10261_336
00925njm 22002777a 4500
dc
Benito, Gerardo
author
Sánchez Moya, Yolanda
author
Sopeña, Alfonso
author
2003-03-17
This paper details the sedimentology of high-stage flood deposits, with the definition of sedimentary environments and their characteristic sequences, along two bedrock reaches of the Tagus River (Central Spain). High-stage flood deposits accumulated in bedrock canyons include slackwater flood deposits (SWD) and other types of deposits located at flow separation zones and associated with slow-moving flow (<1 m s−1). These flood deposits are common indirect indicators of flood stages used in palaeoflood studies for estimating the discharges associated with Quaternary floods. Depositional environments of flood deposits include (1) channel widening, (2) canyon expansion, (3) bedrock obstacles, and (4) backflooded areas along tributary streams. These flood deposits can be found associated with other non-fluvial environments, namely aeolian reworked and slope washflow facies. Channel widening, due to flood stage variations, comprises internal and external zones of the channel margins, and their characteristic sequences contain similar facies to those of alluvial floodplains. Canyon expansion environments favour vertical accretion of slackwater units and the development of flood deposit benches, which contain four sequences related to bench elevation and distance from the channel's main thread of flow. At the lee side of bedrock obstacles, characteristic sedimentary sequences are dominated by reverse flow structures (e.g. climbing ripples migrating upstream) due to eddies with a high sand concentration. Flood deposits located within tributary mouths contain typical sequences of reworked floodplain deposits. Backflooding of tributaries during flood stages produces deposition from suspension of sand, silt and clay within three sequences characterised by non-structure or parallel lamination and intense bioturbation. A better understanding of the flood deposit sequences may contribute to the characterisation of flood magnitudes and flood hydraulics and can also be applied to some ancient depositional environments.
Sedimentary Geology 157(1-2): 107-132
0037-0738
http://hdl.handle.net/10261/12885
10.1016/S0037-0738(02)00196-3
Palaeoflood hydrology
Palaeoflood sedimentology
Slackwater flood deposits
Spain
Sedimentology of high-stage flood deposits of the Tagus River, Central Spain